The present invention relates to a CRT (cathode-ray tube) drive control circuit for controlling a beam current.
An ABL (automatic beam limiter) is arranged in a conventional TV receiver to limit a beam current flowing in the CRT to a predetermined level. A brightness-ABL and a contrast-ABL (or picture-ABL) are known as conventional ABL circuits. The brightness-ABL detects an average beam current of the CRT and decreases a brightness level when a detected beam current level is high. The contrast-ABL decreases a contrast level when a level of an average beam current of the CRT is high.
When the brightness-ABL is operated, an image near dark level becomes black and thus the resolution of the image is degraded. In addition to this disadvantage, changes of a ratio of luminance to chroma often renders a dark flesh tone. On the other hand, in the contrast-ABL, there is neither a deterioration of dark resolution nor a change of a ratio of luminance to chroma. However, in an image having a large average beam current, image contrast becomes insufficient, and a low-quality image results.